Question 1
An engine miss is being diagnosed using a cylinder leakage test.
Technician A says that any cylinder with over 20% leakage has excessive leakage. Tech B
says that air leaking from the tailpipe indicates a cracked cylinder.
A only,
B only,
A & B,
Neither .
CORRECT ANSWER
A only:
If cylinder leakage exceeds 20%, check for air escaping the tailpipe, the PCV valve opening in
the rocker arm cover, and the top of the throttle body or carburetor.
Air leaking from the tailpipe usually indicates an exhaust valve leak
Question 2
During a compression test, a cylinder has 40% of the specified compression reading. When
the tech performs a wet test, the compression reading on this cylinder has 75% of the
specified reading. The cause of the low compression reading could be
Worn piston rings,
1
@THE STUDY VAULT
,A burned exhaust valve,
A bent intake valve,
A worn camshaft lobe,
CORRECT ANSWER
Worn piston rings
If compression increases during a wet test, this indicates worn piston rings. Compression
would not increase if an exhaust valve is burned, intake valve is bent, or camshaft lobe is
worn.
Question 3
The customer complains that the engine cranks but does not start; the first thing to check
should be
Valve train operation,
Battery voltage,
Compression,
Engine vacuum,
CORRECT ANSWER
Valve train operation:
If the engine cranks properly, the battery is not the problem. Compression would not be the
FIRST test, and because engine vacuum is low during a crank, a vacuum test would not be
conclusive.
Question 4
2
@THE STUDY VAULT
,During a cylinder balance test on an engine with fuel injection, one cylinder provides very
little rpm drop.
Tech A says the ignition system may be misfiring on that cylinder.
Tech B says the engine may have an intake manifold vacuum leak.
A only,
B only,
A & B,
Neither ,
CORRECT ANSWER
Both A&B
Both a misfiring ignition system and an intake manifold leak could cause a cylinder to
contribute too little power
Question 5
While discussing basic diagnostic procedures,
Tech A says the most complicated diagnostic tests should be performed first. Tech B says
that you should first question the customer to obtain as much info as possible about the
problem
A,
B,
A & B,
Neither,
CORRECT ANSWER
B
3
@THE STUDY VAULT
, Always attempt the more simple diagnosis first
Question 6
With the engine idling, a vacuum gauge connected to the intake manifold fluctuates (from
15 to 20). These fluctuations may be caused by
Late ignition timing,
Intake manifold vacuum leaks,
A restricted exhaust system,
Sticky valve stems and guides,
CORRECT ANSWER
Sticky valve stems and guides
Question 7
-late ignition timing would result in a low, steady reading
-intake manifold leaks would cause a very low, steady reading
-a restricted exhaust system would cause vacuum to slowly decrease after the engine was
accelerated and held steady
Question 8
Oil is leaking from the crankshaft rear main bearing seal on an engine. Tech A says the oil
seal could be faulty. Tech B says the PCV system may not be functioning.
A,
B,
4
@THE STUDY VAULT
An engine miss is being diagnosed using a cylinder leakage test.
Technician A says that any cylinder with over 20% leakage has excessive leakage. Tech B
says that air leaking from the tailpipe indicates a cracked cylinder.
A only,
B only,
A & B,
Neither .
CORRECT ANSWER
A only:
If cylinder leakage exceeds 20%, check for air escaping the tailpipe, the PCV valve opening in
the rocker arm cover, and the top of the throttle body or carburetor.
Air leaking from the tailpipe usually indicates an exhaust valve leak
Question 2
During a compression test, a cylinder has 40% of the specified compression reading. When
the tech performs a wet test, the compression reading on this cylinder has 75% of the
specified reading. The cause of the low compression reading could be
Worn piston rings,
1
@THE STUDY VAULT
,A burned exhaust valve,
A bent intake valve,
A worn camshaft lobe,
CORRECT ANSWER
Worn piston rings
If compression increases during a wet test, this indicates worn piston rings. Compression
would not increase if an exhaust valve is burned, intake valve is bent, or camshaft lobe is
worn.
Question 3
The customer complains that the engine cranks but does not start; the first thing to check
should be
Valve train operation,
Battery voltage,
Compression,
Engine vacuum,
CORRECT ANSWER
Valve train operation:
If the engine cranks properly, the battery is not the problem. Compression would not be the
FIRST test, and because engine vacuum is low during a crank, a vacuum test would not be
conclusive.
Question 4
2
@THE STUDY VAULT
,During a cylinder balance test on an engine with fuel injection, one cylinder provides very
little rpm drop.
Tech A says the ignition system may be misfiring on that cylinder.
Tech B says the engine may have an intake manifold vacuum leak.
A only,
B only,
A & B,
Neither ,
CORRECT ANSWER
Both A&B
Both a misfiring ignition system and an intake manifold leak could cause a cylinder to
contribute too little power
Question 5
While discussing basic diagnostic procedures,
Tech A says the most complicated diagnostic tests should be performed first. Tech B says
that you should first question the customer to obtain as much info as possible about the
problem
A,
B,
A & B,
Neither,
CORRECT ANSWER
B
3
@THE STUDY VAULT
, Always attempt the more simple diagnosis first
Question 6
With the engine idling, a vacuum gauge connected to the intake manifold fluctuates (from
15 to 20). These fluctuations may be caused by
Late ignition timing,
Intake manifold vacuum leaks,
A restricted exhaust system,
Sticky valve stems and guides,
CORRECT ANSWER
Sticky valve stems and guides
Question 7
-late ignition timing would result in a low, steady reading
-intake manifold leaks would cause a very low, steady reading
-a restricted exhaust system would cause vacuum to slowly decrease after the engine was
accelerated and held steady
Question 8
Oil is leaking from the crankshaft rear main bearing seal on an engine. Tech A says the oil
seal could be faulty. Tech B says the PCV system may not be functioning.
A,
B,
4
@THE STUDY VAULT
